mark@sickkids.UUCP (Mark Bartelt) (01/29/88)
Quick IBM PC question, for anyone who may know the answer ... I'm planning
to buy a 640k XT clone motherboard of some sort, and would prefer to get one
of the so-called turbo boards (the ones that, optionally, run at 8 MHz).
With one exception, all the ones I've been able to find thus far provide only
a dip switch to select between the standard clock rate and the 8 MHz clock.
I have managed to locate one dealer who sells a different type of turbo board.
It will allegedly switch between the two in response to some magic keystroke,
but the people who sell this don't know exactly what the code that does this
actually *does* to select one clock or the other. I need to know since I'm
not a DOS user; we use one or another flavour of UNIX on our XTs. But sadly,
the people who sell the "magic keystroke" type of turbo board are, like nearly
all computer retailers, terribly unknowledgeable about the products they sell.
Certainly not in the wizard category, anyway. Presumably all I need to do in
order to change clocks is "outb someport,somevalue". But they can't tell me
what the "someport" and "somevalue"(s) are. Sigh.
So ... Does anyone out there know of a local source for XT turbo boards that
(1) can switch clocks under software control, AND (2) come with documentation
that tells one how to do it (or, is sold by someone who actually knows)?
If not, I may have to disassemble the "magic keystroke" code. Not a fun way
to spend a day ...
As usual, thanks in advance.
Mark Bartelt
Hospital for Sick Children, Toronto
416/598-6442
{utzoo,decvax,ihnp4}!sickkids!markclewis@spectrix.UUCP (Chris R. Lewis) (01/29/88)
In article <84@sickkids.UUCP> mark@sickkids.UUCP (Mark Bartelt) writes: >Quick IBM PC question ... >I have managed to locate one dealer who sells a different type of turbo board. >It will allegedly switch between the two in response to some magic keystroke, >but the people who sell this don't know exactly what the code that does this >actually *does* to select one clock or the other. >...Presumably all I need to do in >order to change clocks is "outb someport,somevalue". But they can't tell me >what the "someport" and "somevalue"(s) are. Sigh. You should be very careful with purchasing any XT boards if you wish to be able to change clock speed by program control. Most of the boards I'm familiar with (STM products) do this with a parallel bit on the keyboard controller. The keyboard controller is usually a single chip CPU that contains mask ROM, lots of parallel I/O etc. An Intel 8047 I think. The ROM does all of the keyboard decoding, debounce and generates the keyboard scan codes. When it sees the hot key sequence, it merely flips a bit that changes the main CPU clock. In laptops it also quite frequently has an analog output to adjust brightness. Unfortunately, the main CPU CANNOT get at the I/O ports on the keyboard controller. The ol' "you can't get there from here" problem) Thus, the only way to change speed is via the keyboard, but not by program. In contrast, an Intel 386 can do it by program control. The technical manuals for the board should make this clear. -- Chris Lewis, Spectrix Microsystems Inc, UUCP: {uunet!mnetor, utcsri!utzoo, lsuc, yunexus}!spectrix!clewis Phone: (416)-474-1955
daveb@geac.UUCP (David Collier-Brown) (01/30/88)
In article <416@spectrix.UUCP> clewis@spectrix.UUCP (Chris R. Lewis) writes: >In article <84@sickkids.UUCP> mark@sickkids.UUCP (Mark Bartelt) writes: >>Quick IBM PC question ... >>I have managed to locate one dealer who sells a different type of turbo board. >>It will allegedly switch between the two in response to some magic keystroke, >Unfortunately, the main CPU CANNOT get at the I/O ports on the keyboard >controller. The ol' "you can't get there from here" problem) Thus, >the only way to change speed is via the keyboard, but not by program. Fortunately, that isn't the only way to do it. Its just a cheap way. Max Southall at Micro/Access (max@lethe.uucp) has boards which switch speed in rational and useful ways, notably when one presses the "crash MS-DOS" key-sequence or when the board has to slow down for a slower peripheral (floppy drives). He's also good about showing how things work (plug!). --dave (I'm biased, I have one of his CPM Machines) c-b -- David Collier-Brown. {mnetor yunexus utgpu}!geac!daveb Geac Computers International Inc., | Computer Science loses its 350 Steelcase Road,Markham, Ontario, | memory (if not its mind) CANADA, L3R 1B3 (416) 475-0525 x3279 | every 6 months.